Hydrogen-production power supply system and control method therefor

Abstract

Disclosed in the present application are a hydrogen-production power supply system and a control method therefor. The system comprises a transformer, a main power branch, an auxiliary power branch, at least one set of energy storage branches, and a busbar, wherein a primary winding of the transformer is coupled to an alternating-current power grid, and a secondary winding of the transformer is coupled to an input terminal of the main power branch; an output terminal of the main power branch is coupled to an off-grid hydrogen production device; the auxiliary power branch is coupled between the secondary winding and the busbar; the energy storage branches are all coupled to the busbar; the main power branch comprises at least one uncontrolled rectifier circuit and at least one chopper circuit, the uncontrolled rectifier circuit being used for converting into direct currents alternating currents that are output by the transformer, thereby saving costs, and the chopper circuits being used for adjusting the voltage of the direct currents to a voltage required by a load of a chopper branch; the auxiliary power branch is used for outputting power to the busbar and performing power exchange with the alternating-current power grid, thereby improving the capability of responding to the alternating-current power grid; and the energy storage branches are used for pre-storing and releasing electric energy by means of the busbar, thereby improving the system stability.

Description

A hydrogen production power system and its control method Technical Field

[0001] This application relates to the field of new energy hydrogen production technology, and in particular to a hydrogen production power system and its control method. Background Technology

[0002] As a clean, carbon-free, flexible, efficient, and versatile secondary energy source and an important industrial raw material, hydrogen energy has attracted widespread attention. Off-grid hydrogen production technology utilizes new energy power generation systems to produce green hydrogen energy. However, these systems, such as wind power or photovoltaic power generation systems, are intermittent, random, and fluctuating, making them unable to directly supply power to the hydrogen production system. The hydrogen production power supply, as the core equipment connecting the off-grid hydrogen production equipment and the new energy power grid, directly affects the efficiency and safety of the entire hydrogen production system due to its control performance and reliability.

[0003] Currently, the most commonly used hydrogen production equipment is the electrolyzer, including alkaline water electrolyzers and PEM (proton exchange membrane) water electrolyzers. The mainstream hydrogen production capacity of current alkaline electrolyzers is 1000 Nm³. 3 / h, maximum capacity is 5000Nm 3 The load change rate is relatively slow, typically between 1% and 5% of the rated power per minute. The mainstream capacity for PEM electrolytic cells is 200 Nm³. 3 / h, maximum capacity is 500 Nm 3 / h, the load change speed is relatively fast, and the load change rate per minute can reach 10%~20% of the rated power.

[0004] Existing large-capacity hydrogen production power systems typically lack grid support capabilities, preventing large-capacity electrolyzers from producing hydrogen off-grid. Furthermore, the load change rate of electrolyzers is usually subject to specific limitations; under off-grid hydrogen production conditions, existing hydrogen production power sources cannot respond to rapid changes in the renewable energy grid by adjusting the hydrogen production load. Summary of the Invention

[0005] The main objective of this application is to provide a hydrogen production power system and its control method, which aims to utilize a main power branch and an auxiliary power branch to construct a new hydrogen production power system to improve the response capability to grid fluctuations.

[0006] To achieve the above objectives, this application proposes a hydrogen production power system for supplying power to off-grid hydrogen production equipment, comprising: a transformer, a main power branch, an auxiliary power branch, at least one set of energy storage branches, and a busbar; the transformer includes a primary winding and a secondary winding, the primary winding being coupled to an AC power grid, and the secondary winding being coupled to the input terminal of the main power branch; the output terminal of the main power branch is coupled to the off-grid hydrogen production equipment; the auxiliary power branch is coupled between the secondary winding and the busbar; the energy storage branches are all coupled to the busbar; the main power branch includes at least one set of uncontrolled rectifier circuits and at least one set of chopper circuits, the uncontrolled rectifier circuits being used to convert the AC power output from the transformer into DC power, and the chopper circuits being used to adjust the voltage of the DC power to the voltage required by the load of the chopper branch; the auxiliary power branch is used to output power to the busbar and interact with the AC power grid; the energy storage branches are used to pre-store and release electrical energy through the busbar.

[0007] Furthermore, the input terminal of the uncontrolled rectifier circuit is configured as the input terminal of the main power branch, and the output terminal is coupled to the busbar; the input terminal of the chopper circuit is coupled to the busbar, and the output terminal is configured as the output terminal of the main power branch.

[0008] Furthermore, the input terminal of the uncontrolled rectifier circuit is configured as the input terminal of the main power branch, and the output terminal is directly connected to the input terminal of the chopper circuit; the output terminal of the chopper circuit is configured as the output terminal of the main power branch.

[0009] Furthermore, the uncontrolled rectifier circuit includes at least one set of diode-based three-phase bridge circuits; the diode-based three-phase bridge circuit includes three bridge arms, each bridge arm including a first diode and a second diode connected in series; the positive terminal of the first diode is coupled to the negative terminal of the second diode and forms the midpoint of the bridge arm; the midpoint of the bridge arm is configured as the input terminal of the uncontrolled rectifier circuit and coupled to the secondary winding of the transformer, and the negative terminal of the first diode and the positive terminal of the second diode are configured as the output terminal of the uncontrolled rectifier circuit to output DC power.

[0010] Furthermore, the auxiliary power branch includes at least one set of PWM rectifier circuits; the PWM rectifier circuits are used to adjust the power output to the bus in response to frequency fluctuations of the AC power grid; and to adjust the target voltage value of the bus in response to voltage amplitude fluctuations of the AC power grid, so as to keep the active power output from the auxiliary power branch to the bus constant; and to inject short-circuit current into the AC power grid in response to a short circuit in the AC power grid.

[0011] Furthermore, the energy storage branch includes at least one energy storage device, which is a battery pack or a supercapacitor pack.

[0012] Furthermore, the energy storage branch also includes a voltage regulating circuit; the voltage regulating circuit is coupled between the energy storage device and the busbar; the voltage regulating circuit is used to convert the voltage of the busbar into the voltage required by the energy storage device, or to convert the voltage of the energy storage device into the voltage of the busbar, so as to pre-store electrical energy for the energy storage device or enable the energy storage device to output electrical energy to the busbar.

[0013] Furthermore, the at least one set of energy storage branches includes at least one set of energy storage branches with battery packs as energy storage devices and at least one set of energy storage branches with supercapacitor packs as energy storage devices.

[0014] Furthermore, the transformer is a three-winding transformer, and the secondary winding includes a first secondary winding and a second secondary winding; the first secondary winding is coupled to the input terminal of the main power branch, and the second secondary winding is coupled to the input terminal of the auxiliary power branch; the maximum voltage amplitude of the first secondary winding is less than 80% of the maximum voltage amplitude of the second secondary winding.

[0015] Furthermore, a high-pass filter is coupled between the AC power grid and the primary winding of the transformer to filter out the target harmonic components generated on the AC side of the uncontrolled rectifier circuit.

[0016] This application also provides a control method for a hydrogen production power system, comprising: starting an auxiliary power branch and controlling the bus voltage to a target voltage threshold; pre-charging an energy storage branch and controlling the energy reserve of the energy storage branch to a pre-charge amount; starting the main power branch and controlling the off-grid hydrogen production equipment to maintain operation in a first hydrogen production mode; the auxiliary power branch operating in active mode and dynamically adjusting the bus voltage; and the energy storage branch and the chopper circuit adjusting the hydrogen production of the off-grid hydrogen production equipment in the event of voltage fluctuations in the bus.

[0017] Furthermore, the target voltage threshold is greater than or equal to the product of the maximum amplitude of the transformer secondary winding output voltage and a first preset multiple; the pre-charge amount is configured as the product of the total capacity of the energy storage branch and a first preset ratio; the first hydrogen production mode is configured as the load of the off-grid hydrogen production equipment is less than or equal to the product of the rated load and a second preset ratio; the active power mode is the output of active power from the auxiliary power branch to the busbar; in the case of pre-charging the energy storage branch, the operating power of the AC grid does not exceed the charging power of the energy storage branch.

[0018] Furthermore, the energy storage branch and chopper circuit adjust the hydrogen production of the off-grid hydrogen production equipment when the voltage of the busbar fluctuates, including: if the voltage fluctuation of the busbar does not exceed the first fluctuation duration, the energy storage branch with a supercapacitor bank as the energy storage device balances the voltage fluctuation by charging and discharging the supercapacitor bank; if the voltage fluctuation of the busbar exceeds the first fluctuation duration but does not exceed the second fluctuation duration, the energy storage branch with a battery bank balances the voltage fluctuation by charging and discharging the battery bank; if the voltage fluctuation of the busbar exceeds the second fluctuation duration but does not exceed the third fluctuation duration, the chopper circuit reduces or increases the active power output to the off-grid hydrogen production equipment to balance the voltage fluctuation and reduce or increase the hydrogen production of the off-grid hydrogen production equipment.

[0019] Furthermore, it also includes: the auxiliary power branch performs closed-loop control on the reactive power injected into the AC grid based on the reactive power of the primary winding of the transformer, and controls the reactive power of the primary winding of the transformer to the target value; detects and extracts the target harmonics of the primary winding of the transformer, and the auxiliary power branch uses internal mode control or proportional resonance control to suppress the target harmonics.

[0020] Furthermore, it also includes: the auxiliary power branch adopts a virtual synchronous machine algorithm to provide inertia support and reactive power support for the AC grid; the virtual synchronous machine algorithm is characterized by the auxiliary power branch simulating the inertia and damping characteristics of a synchronous engine when executing the virtual synchronous machine algorithm, so that the AC voltage characteristics of the hydrogen production power system tend to be similar to the voltage characteristics of the synchronous engine power generation system.

[0021] Furthermore, it also includes: generating a target phase angle value and a given AC voltage amplitude value for the PWM rectifier circuit based on the virtual synchronous machine algorithm; presetting a target active power value and generating an incremental AC voltage amplitude value based on the actual transmitted active power; generating a target AC voltage amplitude value based on the sum of the given AC voltage amplitude value and the incremental AC voltage amplitude value; generating a reference voltage vector using a dual closed-loop control architecture of an outer AC voltage loop and an inner current loop based on the target AC voltage amplitude value and the target phase angle value; controlling the on and off of the switching devices in the PWM rectifier circuit based on the reference voltage vector; adjusting the output power or input power of the energy storage branch based on the target AC voltage amplitude value; and adjusting the hydrogen production of the off-grid hydrogen production equipment and maintaining the voltage of the busbar stable based on the target AC voltage amplitude value.

[0022] The technical solution of this application adopts a hydrogen production power system with a main power branch and an auxiliary power branch architecture of an uncontrolled rectifier circuit, which significantly reduces the device cost of the main power branch. At the same time, the auxiliary power branch, chopper circuit and energy storage branch are used to regulate the bus voltage and improve the response capability of the hydrogen production power system to the AC power grid. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0024] Figure 1 is a system architecture diagram of Embodiment 1 provided in this application;

[0025] Figure 2 is a system architecture diagram of Embodiment 2 provided in this application;

[0026] Figure 3 is a system architecture diagram of Embodiment 3 provided in this application;

[0027] Figure 4 is a system architecture diagram of Embodiment 4 provided in this application;

[0028] Figure 5 is a schematic diagram of the uncontrolled rectifier circuit 21 provided in this application;

[0029] Figure 6 is a schematic diagram of the PWM rectifier circuit 31 provided in this application;

[0030] Figure 7 is a schematic diagram of the DC-DC converter circuit provided in this application;

[0031] Figure 8 is a schematic diagram of the high-pass filter provided in this application;

[0032] Figure 9 is a flowchart of the control method provided in this application;

[0033] Figure 10 is a flowchart of a voltage fluctuation control method provided in this application;

[0034] Figure 11 is a diagram of the voltage and current dual closed-loop control architecture of the auxiliary power branch 30 provided in this application;

[0035] Figure 12 is a schematic diagram of the virtual synchronous machine control architecture provided in this application.

[0036] Explanation of icon numbers:

[0037] 10. Transformer; 20. Main power branch; 21. Uncontrolled rectifier circuit; 211. Diode-based three-phase bridge circuit; 22. Chopper circuit; 221. Two-level three-phase bridge AC-side parallel circuit; 222. Dual active bridge resonant DC-DC converter circuit; 2221. Active full-bridge unit; 2222. High-frequency transformer unit with resonant devices; 223. Two-level three-phase bridge-diode rectifier-chopper circuit; 30. Auxiliary power branch; 31. PWM Rectifier circuit; 311, Two-level three-phase bridge circuit; 312, Three-level three-phase bridge circuit; 3121, First controllable unit; 3122, Second controllable unit; 40, Energy storage branch; 41, Battery energy storage branch; 411, Battery pack; 412, Battery voltage regulation circuit; 42, Capacitor energy storage branch; 421, Supercapacitor pack; 422, Capacitor voltage regulation circuit; 50, Busbar; 51, Busbar positive terminal; 52, Busbar negative terminal; 60, High-pass filter.

[0038] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Embodiments of the present invention

[0039] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0040] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0041] It should be understood that, in the following description, "circuit" refers to a conductive loop consisting of at least one element or sub-circuit connected by an electrical or electromagnetic link. When an element or circuit is said to be "connected to" or "coupled to" another element, or when an element / circuit is said to be "connected" between two nodes, it can be directly coupled to or connected to the other element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there are no intermediate elements between them.

[0042] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0043] Due to limitations in the load regulation speed of electrolyzers, existing hydrogen production power systems cannot fully respond to the demands of the renewable energy grid when supporting the grid. Furthermore, alkaline hydrogen production electrolyzers, especially large-capacity ones, typically use thyristor-based rectifier circuits for their power supplies. These power supplies generate significant harmonics, reducing the system's power factor and increasing external losses. Additionally, when thyristor-based hydrogen production power supplies are used in high-power scenarios, on-load voltage regulation devices are required to reduce harmonics, which severely impacts the system's response time. PEM electrolyzers typically use converters with IGBTs (insulated-gate bipolar transistors) as the main power devices for hydrogen production, but using IGBT-based power supplies significantly increases the overall cost of the hydrogen production system. Since the load change rate of electrolyzers is usually limited, under certain operating conditions, existing hydrogen production power supplies cannot respond to the rapid changes in the renewable energy grid by adjusting the hydrogen production load. Frequent start-ups and shutdowns of the electrolyzers will severely affect the equipment's lifespan.

[0044] In view of this, embodiments of this application provide a hydrogen production power system that can utilize energy storage devices combined with the load regulation characteristics of the electrolyzer itself and respond to changes in grid frequency and voltage. The following is a detailed description with reference to the accompanying drawings.

[0045] Please refer to Figures 1-4, which are schematic diagrams of the hydrogen production power system architecture. An embodiment of this application provides a hydrogen production power system including a transformer 10, a main power branch 20, an auxiliary power branch 30, at least one set of energy storage branches 40, and a busbar 50. The transformer 10 includes a primary winding and a secondary winding. The primary winding is coupled to the AC power grid, and the secondary winding is coupled to the input terminal of the main power branch 20. The output terminal of the main power branch 20 is coupled to an off-grid hydrogen production device. The auxiliary power branch 30 is coupled between the secondary winding and the busbar 50. All energy storage branches 40 are coupled to the busbar. The main power branch 20 includes at least one set of uncontrolled rectifier circuits 21 and at least one set of chopper circuits 22. The rectifier circuit 21 is used to convert the AC power output from the transformer 10 into DC power, and the chopper circuit 22 is used to adjust the voltage of the DC power to the voltage required by the load of the chopper circuit 22; the AC power grid includes a wind power generation system and / or a photovoltaic power generation system; the off-grid hydrogen production equipment includes an electrolyzer; the auxiliary power branch 30 is used to output power to the busbar 50 and interact with the AC power grid; the energy storage branch 40 stores and releases electrical energy through the busbar 50; the above system uses the auxiliary power branch 30 and the energy storage branch 40 to regulate the voltage of the busbar 50 to absorb and smooth the fluctuations of the AC power grid.

[0046] FIG. 1 is a structural diagram of the system according to the first embodiment provided by the present application. As shown in FIG. 1, in this embodiment, the transformer 10 is a three-winding transformer, whose primary winding is coupled to an AC power grid, and whose secondary windings include a first secondary winding A and a second secondary winding B, wherein the first secondary winding A is coupled to a main power branch 20, and the second secondary winding B is coupled to an auxiliary power branch 30; the auxiliary power branch 30 includes a PWM (pulse width modulation) rectifier circuit 31; the energy storage branch 40 includes a battery energy storage branch 41 and a capacitor energy storage branch 42, wherein the battery energy storage branch 41 includes a battery pack 411 and a battery voltage regulating circuit 412, and the capacitor energy storage branch 42 includes a supercapacitor pack 421 and a capacitor voltage regulating circuit 422; the positive busbar 51 is coupled to the positive output terminal of the uncontrolled rectifier circuit 21, the positive output terminal of the PWM rectifier circuit 31, the positive terminal of the battery energy storage branch 41, the positive terminal of the capacitor energy storage branch 42, and the positive input terminal of the chopper circuit 22, respectively; the negative busbar 52 is coupled to the negative output terminal of the uncontrolled rectifier circuit 21, the negative output terminal of the PWM rectifier circuit 31, the negative terminal of the battery energy storage branch 41, the negative terminal of the capacitor energy storage branch 42, and the negative input terminal of the chopper circuit 22, respectively. In the above structure, the auxiliary power branch 30 uses the PWM rectifier circuit 31 to exchange active and reactive power with the AC power grid, the chopper circuit 22 adjusts the operating power of the electrolyzer, and the energy storage branch 40 uses the battery pack 411 and the supercapacitor pack 421 for charging and discharging. By regulating the DC voltage of the busbar 50, rapid absorption and stabilization of new energy power grid fluctuations and orderly regulation of the electrolyzer load are achieved.

[0047] In the first embodiment described above, the voltage amplitude of the first secondary winding A is less than 80% of the maximum voltage amplitude of the second secondary winding. Denote the AC phase voltage u of the first secondary winding A g has an amplitude of U grm , the AC phase voltage u of the second secondary winding B aux has an amplitude of U auxrm , the two satisfy U auxrm =kU grm , wherein 0<k<0.8. When the AC phase voltage u of the first secondary winding A g has an amplitude of U grm , the DC voltage range output by the uncontrolled rectifier circuit 21 is when the leakage reactance of the transformer 10 is not considered. When the AC phase voltage u of the second secondary winding B aux has an amplitude of U auxrm , according to the working characteristics of the PWM rectifier circuit 31, the DC voltage u output by the PWM rectifier circuit 31 dc usually needs to satisfy When both the PWM rectifier circuit 31 and the uncontrolled rectifier circuit 21 need to inject active power into the bus 50 simultaneously, the DC voltage u output by the PWM rectifier circuit 31... dc The minimum value must be less than the lower limit of the DC voltage output by the uncontrolled rectifier circuit 21. , that is .

[0048] In the above embodiment 1, referring to FIG1, the hydrogen production power system further includes a high-pass filter 60, which is coupled between the AC power grid and the primary winding of the three-winding transformer, and is used to filter out the target harmonic components generated by the AC side of the uncontrolled rectifier circuit 21. In some embodiments, specifically, the target harmonic components are AC harmonic components of the 17th order and above.

[0049] Figure 2 is a system framework diagram of Embodiment 2 provided in this application. As shown in Figure 2, the system architecture in this embodiment is roughly the same as that in Embodiment 1 above, but the capacitor energy storage branch 42 in this embodiment only includes the supercapacitor group 421. By directly coupling the supercapacitor group 421 to the busbar 50, the energy utilization efficiency of the supercapacitor group 421 is improved.

[0050] Figure 3 is a system framework diagram of Embodiment 3 provided in this application. As shown in Figure 3, the system architecture in this embodiment is similar to that in Embodiment 1 above. However, in this embodiment, the transformer 10 is a multi-winding transformer, and its secondary winding includes a first secondary winding A, a second secondary winding B, and a third secondary winding C. The main power branch 20 includes two sets of uncontrolled rectifier circuits and M sets of chopper circuits 22, where M is a natural number greater than 0. The output terminals of the two sets of uncontrolled rectifier circuits 21 are connected in parallel to the busbar 50, and the input terminals of the M sets of chopper circuits 22 are connected in parallel to the busbar 50, and their output terminals are connected in parallel to the input terminal of the electrolytic cell. The first secondary winding A and the second secondary winding B in the transformer 10 are respectively coupled to the input terminals of the two sets of uncontrolled rectifier circuits 21, and the third secondary winding C is coupled to the input terminal of the auxiliary power branch 30. In this embodiment, the winding connection types of the first secondary winding A and the second secondary winding B are Y-type and Δ-type, respectively. The phase difference of the terminal voltages on the AC side of the two sets of uncontrolled rectifier circuits 21 is 30°. By connecting the windings in parallel with phase shift, the harmonic components injected into the AC power grid and the busbar 50 by the uncontrolled rectifier circuit 21 are reduced, and the harmonic suppression components of the auxiliary power branch 30 are lowered. It should be understood that although the energy storage branch 40 in this embodiment only includes the capacitor energy storage branch 42, it can also be set up according to the energy storage branch 40 in the above embodiment one or two.

[0051] Figure 4 is a system framework diagram of Embodiment 4 provided in this application. As shown in Figure 4, the system architecture in this embodiment is roughly the same as that in the above embodiments. However, in this embodiment, the transformer 10 is an isolation transformer with only one set of secondary windings, which are coupled to both the main power branch 20 and the auxiliary power branch 30. Furthermore, the uncontrolled rectifier circuit 21 in the main power branch 20 is directly connected to the chopper circuit 22, without being indirectly coupled through the busbar 50. In this embodiment, the auxiliary power branch 30 provides reactive power support to the AC grid and performs low-order harmonic suppression, achieving high power factor and low grid harmonic operation of the hydrogen production power system. In addition, in this embodiment, the auxiliary power branch 30, in conjunction with the energy storage branch 40, absorbs and smooths the instantaneous power fluctuations generated by the new energy AC grid, preventing the electrolyzer from frequently starting and stopping due to load changes failing to keep up with the transient fluctuations of the new energy AC grid. When frequency and voltage amplitude fluctuations occur in the new energy AC grid, the main power branch 20 and the auxiliary power branch 30 work together to provide frequency support and voltage stabilization control for the AC grid through the coordinated action of energy storage devices and electrolytic cell loads.

[0052] Figure 5 is a schematic diagram of the uncontrolled rectifier circuit 21 provided in this application. In the various hydrogen production power system architectures described above, the uncontrolled rectifier circuit 21 includes at least one set of first bridge circuits. Exemplarily, the first bridge circuit can be a diode-based three-phase bridge circuit 211. As shown in Figure 5, taking an uncontrolled rectifier circuit 21 composed of multiple sets of diode-based three-phase bridge circuits 211 connected in parallel as an example, referring to Figures 5 and 1, each diode-based three-phase bridge circuit 211 includes three bridge arms, each bridge arm including a first diode D1 and a second diode D2 connected in series, wherein the positive terminal of the first diode D1 is coupled to the negative terminal of the second diode D2 and forms the midpoint of the bridge arm. The midpoint of the bridge arm is configured as the input terminal of the uncontrolled rectifier circuit 21, coupled to the secondary winding of the transformer 10, i.e., the midpoint of the bridge arm is the AC side; the negative terminal of the first diode D1 and the positive terminal of the second diode D2 are configured as the output terminal of the uncontrolled rectifier circuit 21 to output DC power, coupled to the busbar 50, which is the DC side. Multiple diode-based three-phase bridge circuits 211 are connected in parallel on their AC sides to form the input terminal of the main power branch 20, and connected in parallel on their DC sides to form the output terminal of the uncontrolled rectifier circuit 21. Since the uncontrolled rectifier circuits 21 provided in this application are all composed of low-cost diodes, compared to hydrogen production power systems that use PWM rectifier circuits 31 or thyristors or high-power converters, the hydrogen production power system in this application is low-cost, has a simple power circuit structure, and is easy to troubleshoot.

[0053] Figure 6 is a schematic diagram of the PWM rectifier circuit 31 provided in this application, including a two-level three-phase bridge circuit 311 and a three-level three-phase bridge circuit 312. In the above-mentioned hydrogen production power system architectures, the auxiliary power branch 30 includes at least one set of PWM rectifier circuits 31. The PWM rectifier circuit 31 can be a two-level three-phase bridge circuit 311 or a three-level three-phase bridge circuit 312 based on fully controlled devices, wherein the fully controlled devices are IGBTs, IGCTs, or GTOs. As shown in Figure 6, the AC side of the two-level three-phase bridge circuit 311 or the three-level three-phase bridge circuit 312 has three-phase terminals a, b, and c, and the DC side has two-level PN and three-level PON, respectively, as the output terminals of the PWM rectifier circuit 31.

[0054] Taking the application of the two-level three-phase bridge circuit 311 in Embodiment 1 as an example, referring to Figures 6 and 1, the two-level three-phase bridge circuit 311 includes three bridge arms. Each bridge arm includes a first fully controlled device T1 and a second fully controlled device T2 connected in series. The positive terminal of the first fully controlled device T1 is coupled to the negative terminal of the second fully controlled device T2, forming the midpoint of the bridge arm. The midpoint of the bridge arm is coupled to the secondary winding of the transformer 10 through an inductor L. A capacitor C is coupled between the negative terminal of the first fully controlled device T1 and the positive terminal of the second fully controlled device T2, and is respectively coupled to the positive terminal 51 and the negative terminal 52 of the busbar.

[0055] Taking the application of the three-level three-phase bridge circuit 312 in Embodiment 1 as an example, referring to Figures 6 and 1, the three-level three-phase bridge circuit 312 includes three bridge arms. Each bridge arm includes a first controllable unit 3121 and a second controllable unit 3122. The first controllable unit 3121 includes a first switch K1, a second switch K2, and a first clamping diode Z1. The negative terminal of the first switch K1 in the conduction direction is configured as the first end of the first controllable unit 3121. The positive terminal of the first switch K1 in the conduction direction is coupled to the negative terminal of the second switch K2 in the conduction direction. The positive terminal of the second switch K2 in the conduction direction is configured as the second end of the first controllable unit 3121. The positive terminal of the first clamping diode Z1 is configured as the third end of the first controllable unit 3121, and the negative terminal is coupled between the first switch K1 and the second switch K2. The second controllable unit 3122 includes a third switch K3, a fourth switch K4, and a second clamping diode Z2. The negative terminal of the third switch K3 in the conduction direction is configured as the first terminal of the second controllable unit 3122. The positive terminal of the third switch K3 in the conduction direction is coupled to the negative terminal of the fourth switch K4 in the conduction direction. The positive terminal of the fourth switch K4 in the conduction direction is configured as the second terminal of the second controllable unit 3122. The negative terminal of the second clamping diode Z2 is configured as the third terminal of the second controllable unit 3122, and the positive terminal is coupled between the third switch K3 and the fourth switch K4. The second end of the first controllable unit 3121 and the first end of the second controllable unit 3122 are coupled together to form the midpoint of the bridge arm. The third end of the first controllable unit 3121 and the third end of the second controllable unit 3122 are coupled together. All midpoints of the bridge arms are coupled to the secondary winding of the transformer 10 through an inductor L. A first capacitor C1 and a second capacitor C2 are coupled in series between the first end of the first controllable unit 3121 and the second end of the second controllable unit 3122, and are respectively coupled to the positive terminal 51 and the negative terminal 52 of the busbar. The midpoint of the series connection of the first capacitor C1 and the second capacitor C2 is coupled to any midpoint of the bridge arm.

[0056] Taking the above embodiment 1 as an example, referring to Figures 1 and 6, the auxiliary power branch 30 needs to adjust the DC voltage of the bus 50 according to the AC grid status, the electrolyzer operating conditions, and the status of the battery energy storage branch 41 and the capacitor energy storage branch 42. Under normal operating conditions of the electrolyzer, the auxiliary power branch 30, i.e., the PWM rectifier circuit 31, can provide some active power to the electrolyzer. If the high-voltage side of the hydrogen production power supply, i.e., the primary winding of the transformer 10, has reactive power demand or generates low-order harmonics, the auxiliary power branch 30 can inject reactive power into the AC grid and suppress low-order harmonics, thereby improving the power factor and harmonic characteristics of the hydrogen production power supply system. When the AC power grid experiences frequency fluctuations, the auxiliary power branch 30 can adjust the active power injected into the hydrogen production power system based on the frequency changes. For example, by controlling the fully controlled devices in the two-level three-phase bridge circuit 311 or the three-level three-phase bridge circuit 312, it can reduce or increase the power input to the bus 50 from the PWM rectifier circuit 31, thereby mitigating the impact of AC power grid frequency fluctuations on the bus 50 and providing inertia support for the AC power grid. When the AC power grid experiences voltage amplitude changes, the auxiliary power branch 30 adjusts the target voltage value of the bus 50 based on the voltage amplitude changes and provides reactive power support to the AC power grid, thereby maintaining a constant active power output from the auxiliary power branch 30 to the bus 50. When a short circuit occurs in the AC power grid, the auxiliary power branch 30 can inject a short-circuit current into the AC power grid. The magnitude and duration of the short-circuit current are determined by the power capacity of the auxiliary power branch 30 and the energy storage capacity of the energy storage branch 40. One design parameter scheme is as follows: the minimum power capacity of the auxiliary power branch 30 is 20% of the rated power capacity of the uncontrolled rectifier circuit 21, and the maximum is 50% of the rated power capacity of the uncontrolled rectifier circuit 21.

[0057] Figure 7 is a schematic diagram of the DC-DC converter circuit provided in this application. In the above embodiments, the chopper circuit 22 in the main power branch 20 is used to convert the DC power output by the uncontrolled rectifier circuit 21 into the DC power required by the electrolytic cell. The voltage regulation circuits in the energy storage branch 40, such as the battery voltage regulation circuit 412 and the capacitor voltage regulation circuit 422, are used to convert the voltage on the bus 50 into the charging voltage required by the battery pack 411 and the supercapacitor pack 421, or to convert the discharge voltage of the battery pack 411 and the supercapacitor pack 421 into the target voltage value of the bus 50, so as to maintain the bus 50 to provide a stable operating voltage for the electrolytic cell or to provide inertia support or reactive power support for the AC power grid.

[0058] Figure 7 shows three DC-DC converter circuits: a two-level three-phase bridge AC-side parallel circuit 221, a dual active bridge resonant DC-DC converter circuit 222, and a two-level three-phase bridge-diode rectifier-chopper circuit 223. The two-level three-phase bridge AC-side parallel circuit 221 is based on a two-level three-phase bridge circuit 311. Building upon the structure of the two-level three-phase bridge circuit 311, the DC side of the two-level three-phase bridge circuit 311 is used as one DC port, and the three terminals of the AC side are connected to form a parallel AC-side structure as the other DC port for transmitting DC voltage. The dual active bridge resonant DC-DC converter circuit 222 includes two active full-bridge units 2221 and a high-frequency transformer unit 2222 with resonant devices. Both ports of the active full-bridge unit 2221 are DC ports, and the resonant devices are LLC resonant structures composed of capacitors and inductors. The full-bridge unit 2221 is coupled to both ends of the high-frequency transformer unit 2222 with resonant devices. By adjusting the active devices in the two active full-bridge units 2221, bidirectional power flow can be supported. Simultaneously, the resonant devices can achieve soft-switching, reducing losses. The two-level three-phase bridge-diode rectifier chopper circuit 223 is based on the two-level three-phase bridge circuit 311. One end of the DC side of the two-level three-phase bridge circuit 311 is used as one of the DC ports, and the other end of the AC side is coupled to the midpoint of the three bridge arms of the diode rectifier circuit through the transformer winding. The topology of the diode rectifier circuit is the same as that of the diode-based three-phase bridge circuit 211 provided in this application. In the hydrogen production power system structure described in the above embodiments, the chopper circuit 22 can utilize any of the three DC-DC conversion circuits shown in Figure 7. The voltage regulation circuit in the energy storage branch 40 can preferably utilize the dual active bridge resonant DC-DC conversion circuit 222. It should be understood that the three specific DC-DC conversion circuits shown in Figure 7 are not intended to limit the scope of protection of the claims in this embodiment.

[0059] Figure 8 is a schematic diagram of the high-pass filter provided in this application. As shown in Figure 8, the high-pass filter 60 in the above system architectures can be composed of a first-order, second-order, third-order, or C-type passive filter circuit consisting of a capacitor C, an inductor L, and a resistor R. It should be understood that the schematic diagram of the high-pass filter 60 shown in Figure 8 is not intended to limit the scope of protection of the claims of this application. Any high-pass filter 60 that can filter out the target harmonic components generated on the AC side of the uncontrolled rectifier circuit 21 can be freely selected by those skilled in the art.

[0060] This application also proposes a control method for a hydrogen production power system. The method includes: activating an auxiliary power branch 30 to control the voltage of the busbar 50 to a target voltage threshold; pre-charging an energy storage branch 40 and controlling the energy reserve of the energy storage branch 40 to a pre-charge amount; activating a main power branch 20 to control the off-grid hydrogen production equipment to maintain a first hydrogen production mode; the auxiliary power branch 30 operating in active mode to dynamically adjust the voltage of the busbar 50; and the energy storage branch 40 and the chopper circuit 22 adjusting the hydrogen production of the off-grid hydrogen production equipment in response to voltage fluctuations in the busbar 50. The target voltage threshold is greater than or equal to the product of the maximum amplitude of the output voltage of the secondary winding of the transformer 10 and a first preset multiple, where the first preset multiple is generally set to... The pre-charge amount is configured as the product of the total capacity of the energy storage branch 40 and a first preset ratio, which is generally set to 50%; the first hydrogen production mode is configured as the load of the off-grid hydrogen production equipment is less than or equal to the product of the rated load and a second preset ratio, which is generally set to 50%; the active power mode is configured as the auxiliary power branch 30 outputs active power to the busbar 50; in the case of pre-charging the energy storage branch 40, the operating power of the AC grid does not exceed the charging power of the energy storage branch 40.

[0061] Figure 9 is a flowchart of the control method provided in this application. As shown in Figure 9, the control method includes the following steps: S1: Start the auxiliary power branch 30 and control the voltage of the bus 50 to the target voltage threshold; S2: Limit the AC grid power and precharge the energy storage branch 40; S3: Start the main power branch 20, start the off-grid hydrogen production equipment and maintain the off-grid hydrogen production equipment at a low hydrogen production rate; S4: Release the AC grid power limiting mode and do not control the active power output of the rectifier circuit 21; S5: The auxiliary power branch 30 operates in active mode, and the voltage of the bus 50 is dynamically adjusted; S6: The energy storage branch 40 and the chopper circuit 22 adjust the charging and discharging operation and adjust the hydrogen production rate of the off-grid hydrogen production equipment according to the voltage fluctuation of the bus 50. In the above steps, when precharging the energy storage branch 40, the power output of the AC grid to the hydrogen production power system can be controlled below the charging power of the energy storage branch 40 by selecting the AC grid power mode, so as to prevent the energy storage branch 40 from being overcharged and damaged. Once the energy storage in the energy storage branch 40 reaches the preset pre-charge amount, the output power of the AC grid is increased, causing the uncontrolled rectifier circuit 21 to start outputting active power to the bus 50 or directly to the chopper circuit 22, thereby starting the off-grid hydrogen production equipment. During the hydrogen production process of the off-grid hydrogen production equipment, the auxiliary power branch 30 dynamically adjusts the voltage of the bus 50 by regulating the power of the PWM rectifier circuit 31, in order to provide inertial support and reactive power to the AC grid.

[0062] In the control method of the above-mentioned hydrogen production power system, the energy storage branch 40 and the chopper circuit 22 adjust the hydrogen production of the off-grid hydrogen production equipment when the voltage of the bus 50 fluctuates by performing the following judgment steps: if the voltage fluctuation of the bus 50 does not exceed the first fluctuation duration, the energy storage branch 40, whose energy storage device is a supercapacitor group 421, balances the voltage fluctuation by charging and discharging the supercapacitor group 421; if the voltage fluctuation of the bus 50 exceeds the first fluctuation duration but does not exceed the second fluctuation duration, the energy storage branch 40, whose energy storage device is a battery group 411, balances the voltage fluctuation by charging and discharging the battery group 411; if the voltage fluctuation of the bus 50 exceeds the second fluctuation duration but does not exceed the third fluctuation duration, the chopper circuit 22 reduces or increases the active power output to the off-grid hydrogen production equipment to balance the voltage fluctuation and reduces or increases the hydrogen production of the off-grid hydrogen production equipment.

[0063] Figure 10 is a flowchart of a voltage fluctuation control method provided in this application. As shown in Figure 10, the first fluctuation duration is set to 30 seconds, the second fluctuation duration to 5 minutes, and the third fluctuation duration to 10 minutes. The process for balancing the voltage fluctuation of the bus 50 includes: S601 detecting the voltage fluctuation of the bus 50; S602 charging and discharging the capacitor energy storage branch 42; S603 determining whether the fluctuation time is greater than 30 seconds, if so, executing S604, otherwise executing S605; S604 charging and discharging the battery energy storage branch 41; S60... S606 stops the operation of capacitor energy storage branch 42; S607 determines whether the fluctuation time is greater than 5 minutes, if so, execute S607, otherwise execute S608; S607 adjusts the output power of chopper circuit 22, S608 stops the operation of battery energy storage branch 41; S609 determines whether the fluctuation time is greater than 10 minutes, if so, execute S610, otherwise execute S611; S610 troubleshoots system faults, S611 maintains the output power of chopper circuit 22.

[0064] Based on the control method of the aforementioned hydrogen production power system, the method further includes: The auxiliary power branch 30 performs closed-loop control on the reactive power injected into the AC grid according to the reactive power of the primary winding of the transformer 10, controlling the reactive power of the primary winding of the transformer 10 to a target value; the auxiliary power branch 30 detects and extracts the target harmonics of the primary winding of the transformer 10, and uses internal mode control or proportional resonance control to suppress the target harmonics. The target value is generally set to zero.

[0065] Figure 11 is a diagram of the dual closed-loop control architecture for voltage and current of the auxiliary power branch 30 provided in this application. Taking Embodiment 1 as an example, referring to Figures 1 and 11, the target value of the d-axis component of the AC terminal voltage of the auxiliary power branch 30 is... Compared with actual value The target value of the d-axis component of the inner loop current generated by the closed-loop control circuit The target value of the d-axis component of the current in the PWM rectifier circuit 31 Compared with actual value The d-axis component of the reference voltage vector is generated through the closed-loop control circuit. Target value of the q-axis component of the AC terminal voltage of auxiliary power branch 30 Compared with actual value The target value of the q-axis component of the inner loop current generated by the closed-loop control circuit. The target value of the q-axis component of the current in the PWM rectifier circuit 31 Compared with actual value The q-axis component of the reference voltage vector is generated through the closed-loop control circuit. Usually makes and It implements dual closed-loop control.

[0066] Based on the control method of the above-mentioned hydrogen production power system, it also includes: the auxiliary power branch 30 uses a virtual synchronous machine algorithm to provide inertia support and reactive power support for the AC power grid; the virtual synchronous machine algorithm is characterized by the auxiliary power branch 30 simulating the inertia and damping characteristics of the synchronous engine when executing the virtual synchronous machine algorithm, so that the AC voltage characteristics of the hydrogen production power system tend to the voltage characteristics of the synchronous engine power generation system, so as to smooth the fluctuations of the AC power grid. Specifically, taking Embodiment 1 as an example, the method includes: generating a target phase angle value and a given AC voltage amplitude value for the PWM rectifier circuit 31 according to the virtual synchronous machine algorithm; presetting a target active power value and generating an incremental AC voltage amplitude value based on the actual transmitted active power; generating a target AC voltage amplitude value based on the sum of the given AC voltage amplitude value and the incremental AC voltage amplitude value; generating a reference voltage vector using a dual closed-loop control architecture of an outer AC voltage loop and an inner current loop based on the target AC voltage amplitude value and the target phase angle value; controlling the switching devices in the PWM rectifier circuit 31 to turn on and off according to the reference voltage vector; adjusting the output power or input power of the energy storage branch 40 according to the target AC voltage amplitude value; and adjusting the hydrogen production of the off-grid hydrogen production equipment and maintaining the voltage of the busbar 50 stable according to the target AC voltage amplitude value. The above method executes a virtual synchronization algorithm through the PWM rectifier circuit 31, combined with a dual closed-loop control architecture, to enable the auxiliary power branch 30 to interact with the AC grid, and to work with the energy storage branch 40 and the chopper circuit 22 to maintain the voltage stability of the bus 50.

[0067] Figure 12 is a schematic diagram of the virtual synchronous machine control architecture provided in this application. As shown in Figure 12, J is the virtual inertia coefficient, K... D This is the virtual damping coefficient. P is the power grid reference frequency. ref and Paux These are the given and actual values ​​of the active power transmitted by auxiliary power branch 30, respectively. The target value of the phase angle for the PWM rectifier circuit 31; and These are the setpoint and actual values ​​of the reactive power on the high-voltage side of a multi-winding transformer, respectively. Typically, let... ;K Q This is the AC voltage amplitude adjustment coefficient. The reference amplitude of the grid voltage. The given value for the AC voltage amplitude increment. The target value is the AC voltage amplitude. Based on this control architecture, the hydrogen production power system provided in this application can provide inertia support and reactive power support to the AC power grid.

[0068] The above description is merely an optional embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the inventive concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A hydrogen production power system for supplying power to off-grid hydrogen production equipment, characterized in that, include: Transformer, main power branch, auxiliary power branch, at least one set of energy storage branch and busbar; The transformer includes a primary winding and a secondary winding. The primary winding is used to couple to the AC power grid, and the secondary winding is coupled to the input terminal of the main power branch. The output terminal of the main power branch is used to couple to the off-grid hydrogen production equipment; The auxiliary power branch is coupled between the secondary winding and the busbar; The at least one set of energy storage branches are all coupled to the busbar; The main power branch includes at least one set of uncontrolled rectifier circuits and at least one set of chopper circuits. The uncontrolled rectifier circuits are used to convert the AC power output by the transformer into DC power, and the chopper circuits are used to adjust the voltage of the DC power to the voltage required by the load of the chopper circuit. The auxiliary power branch is used to output power to the busbar and interact with the AC power grid. The energy storage branch is used for pre-storing and releasing electrical energy through the busbar.

2. The hydrogen production power system as described in claim 1, characterized in that, The input terminal of the uncontrolled rectifier circuit is configured as the input terminal of the main power branch, and the output terminal is coupled to the busbar. The input terminal of the chopper circuit is coupled to the busbar, and the output terminal is configured as the output terminal of the main power branch.

3. The hydrogen production power system as described in claim 1, characterized in that, The input terminal of the uncontrolled rectifier circuit is configured as the input terminal of the main power branch, and the output terminal is connected to the input terminal of the chopper circuit. The output terminal of the chopper circuit is configured as the output terminal of the main power branch.

4. The hydrogen production power system as described in claim 1, characterized in that, The uncontrolled rectifier circuit includes at least one set of first bridge circuits; The first bridge circuit includes three bridge arms, each of which includes a first diode and a second diode connected in series. The positive terminal of the first diode is coupled to the negative terminal of the second diode, and a bridge arm midpoint corresponding to the bridge arm is provided between the positive terminal of the first diode and the negative terminal of the second diode. The midpoint of the bridge arm is configured as the input terminal of the uncontrolled rectifier circuit and coupled to the secondary winding of the transformer. The negative terminal of the first diode and the positive terminal of the second diode are configured as the output terminal of the uncontrolled rectifier circuit to output the DC power.

5. The hydrogen production power system as described in claim 1, characterized in that, The auxiliary power branch includes at least one set of PWM rectifier circuits; The PWM rectifier circuit is used to adjust the power output to the bus in response to frequency fluctuations of the AC power grid; and to adjust the target voltage value of the bus in response to voltage amplitude fluctuations of the AC power grid, so as to keep the active power output to the bus from the auxiliary power branch constant. And for injecting short-circuit current into the AC power grid in response to a short circuit in the AC power grid.

6. The hydrogen production power system as described in claim 1, characterized in that, The energy storage branch includes at least one energy storage device, which is a battery pack or a supercapacitor pack.

7. The hydrogen production power system as described in claim 6, characterized in that, The energy storage branch also includes a voltage regulation circuit; The voltage regulation circuit is coupled between the energy storage device and the busbar; The voltage regulating circuit is used to convert the voltage of the busbar into the voltage required by the energy storage device, or to convert the voltage of the energy storage device into the voltage of the busbar, so as to pre-store electrical energy for the energy storage device or enable the energy storage device to output electrical energy to the busbar.

8. The hydrogen production power system as described in claim 6, characterized in that, The at least one set of energy storage branches includes at least one set of energy storage branches with battery packs as energy storage devices and at least one set of energy storage branches with supercapacitor packs as energy storage devices.

9. The hydrogen production power system as described in claim 1, characterized in that, The transformer is a three-winding transformer, and the secondary winding includes a first secondary winding and a second secondary winding. The first secondary winding is coupled to the input terminal of the main power branch, and the second secondary winding is coupled to the input terminal of the auxiliary power branch; The maximum voltage amplitude of the first secondary winding is less than 80% of the maximum voltage amplitude of the second secondary winding.

10. The hydrogen production power system as described in claim 1, characterized in that, Also includes: A high-pass filter is coupled between the AC power grid and the primary winding of the transformer to filter out the target harmonic components generated on the AC side of the uncontrolled rectifier circuit.

11. A control method for a hydrogen production power system, characterized in that, The method for controlling a hydrogen production power system as described in any one of claims 1-10 includes: Start the auxiliary power branch and control the bus voltage to the target voltage threshold; A pre-charged energy storage branch is configured to control the energy reserve of the energy storage branch to be the pre-charge amount. Start the main power branch to control the off-grid hydrogen production equipment to maintain the first hydrogen production mode; The auxiliary power branch operates in active mode, dynamically adjusting the voltage of the busbar. The energy storage branch and chopper circuit adjust the hydrogen production of the off-grid hydrogen production equipment in response to voltage fluctuations in the busbar.

12. The control method as described in claim 11, characterized in that, The target voltage threshold is greater than or equal to the product of the maximum amplitude of the output voltage of the transformer secondary winding and a first preset multiple; The precharge amount is configured as the product of the total capacity of the energy storage branch and a first preset ratio; The first hydrogen production mode is configured such that the load of the off-grid hydrogen production equipment is less than or equal to the product of the rated load and a second preset ratio; The active power mode is configured such that the auxiliary power branch outputs active power to the busbar; When the energy storage branch is pre-charged, the operating power of the AC power grid shall not exceed the charging power of the energy storage branch.

13. The control method as described in claim 11, characterized in that, The energy storage branch and chopper circuit adjust the hydrogen production of the off-grid hydrogen production equipment when the voltage of the busbar fluctuates, including: If the voltage fluctuation of the busbar does not exceed the duration of the first fluctuation, the energy storage device is the energy storage branch of the supercapacitor bank, which balances the voltage fluctuation by charging and discharging the supercapacitor bank. If the voltage fluctuation of the busbar exceeds the first fluctuation duration but does not exceed the second fluctuation duration, then the energy storage device is the energy storage branch of the battery pack, which balances the voltage fluctuation by charging and discharging the battery pack. If the voltage fluctuation of the busbar exceeds the second fluctuation duration but does not exceed the third fluctuation duration, the chopper circuit reduces or increases the active power output to the off-grid hydrogen production equipment to balance the voltage fluctuation and reduce or increase the hydrogen production of the off-grid hydrogen production equipment.

14. The control method as described in claim 11, characterized in that, Also includes: The auxiliary power branch performs closed-loop control on the reactive power injected into the AC grid based on the reactive power of the primary winding of the transformer, and controls the reactive power of the primary winding of the transformer to the target value. The target harmonics of the transformer's primary winding are detected and extracted, and the auxiliary power branch uses internal mode control or proportional resonance control to suppress the target harmonics.

15. The control method as described in claim 11, characterized in that, Also includes: The auxiliary power branch uses a virtual synchronous machine algorithm to provide inertia support and reactive power support for the AC power grid. The virtual synchronizing machine algorithm is characterized by simulating the inertia and damping characteristics of a synchronous engine when the auxiliary power branch executes the virtual synchronizing machine algorithm, so that the AC voltage characteristics of the hydrogen production power system tend to be similar to the voltage characteristics of the synchronous engine power generation system.

16. The control method as described in claim 15, characterized in that, Also includes: The phase angle target value and AC voltage amplitude setpoint of the PWM rectifier circuit are generated according to the virtual synchronous machine algorithm. The active power target value is preset, and the AC voltage amplitude increment setpoint is generated based on the actual transmitted active power. The target value of AC voltage amplitude is generated based on the sum of the given value of AC voltage amplitude and the given value of AC voltage amplitude increment. Based on the target value of AC voltage amplitude and the target value of phase angle, a reference voltage vector is generated using a dual closed-loop control architecture consisting of an AC voltage outer loop and a current inner loop. The switching devices in the PWM rectifier circuit are turned on and off according to the reference voltage vector. The energy storage branch adjusts its output power or input power according to the target value of the AC voltage amplitude. The chopper circuit adjusts the hydrogen production of the off-grid hydrogen production equipment according to the target value of the AC voltage amplitude and maintains the voltage of the busbar stable.

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